<template>
    <div class="my-scroll" :class="[scrollState?'prohibit':'allow']" ref="myScroll" @scroll.passive="onScroll($event)" @touchstart="touchStart($event)" @touchmove="touchMove($event)" @touchend="touchEnd($event)"  >
        <div class="scroll-top" :style="{height:top+'px'}">
            <div v-if="aspect==2">
                <p v-if="state==6">
                    下拉刷新
                </p>
                <p v-if="state==1">
                    <i><img :src="Load"/></i>
                    <br/>
                    刷新中
                </p>
                <p v-if="state==2">松开刷新</p>
                <p v-if="state==3">
                    <i><img :src="Load"/></i>
                    <br/>
                    刷新完成
                </p>
            </div>
        </div>
        <!-- top -->
        <div class="scroll-list" :style="{ transform: 'translate3d(0, ' + top + 'px, 0)'}">
            <slot name='scrollList'></slot>
            <div class="scroll-bottom">
                <div v-if="state==4">加载中</div>
                <div v-if="state==5">加载完成</div>
                <div v-if="state==7">没有更多</div>
            </div>
        </div>
    </div>
</template>
<script type="text/javascript">
    import tween from '../lib/tween'
    import Load from '../assets/Load.gif'
    export default {
        name:'vue-scroll',
        props:{
            'page':{
                type:Object,  //counter:当前页  pageStart:开始页数  pageEnd:结束页数  total:总页数
            },
            'onRefresh':{ //刷新回调
                type:Function,
                require:true
            },
            'onPull':{ //加载回调
                type:Function,
                require:true
            },
            'getScrollTop':{ //获取滚动条位置
                type:Function
            },
            'setScrollPage':{ //改变滚动条位置
                type:Function
            },
            'scrollState':{//是否可滑动
                type:Boolean,
                require:true
            }
        },
        data(){
            return {
                Load,
                pageX:0,
                pageY:0,
                state:0,
                scrollPosition:0,
                myScroll:null,
                myScrollList:null,
                top:0,
                aspect:0, //1:向下 2:向上
                listHeight:0,
            }
        },
        created(){

        },
        methods:{
            ScrollTop(top){ //修改滚动条位置
                this.myScroll.scrollTop = top
            },
            /*
             * 刷新中：1
             * 松开刷新：2
             * 刷新完成：3
             * 加载中：4
             * 加载完成：5
             * 下拉刷新：6
             * 没有更多：7
             */
            setState(index){ //修改状态
                this.state = index
                if(index == 5||index == 3){
                    setTimeout(()=>{
                        this.state = 0
                        let timer = null;
                        let that = this;
                        var b=50,c=100,d=100,t=0;
                        cancelAnimationFrame(timer);
                        timer = requestAnimationFrame(function fn() {
                            var oTop = that.top;
                            if (that.top>0) {
                                that.top = Math.ceil(tween.Quart.easeInOut(10,oTop,8,10)) - 15
                                timer = requestAnimationFrame(fn);
                            } else {
                                cancelAnimationFrame(timer);
                                that.top = 0
                            }
                        });
                    },500)
                }
            },
            touchStart(e){ //触摸事件
                this.pageX = e.targetTouches[0].pageX
                this.pageY = e.targetTouches[0].pageY
            },
            touchMove(e){ //触摸滑动事件
                this.scrollPosition = this.myScroll.scrollTop //获取滚动条位置
                if(this.scrollState&&e.targetTouches[0].pageY>this.pageY){ //向上滑动
                    this.aspect = 2
                    if(this.myScroll.scrollTop==0){
                        let diff = e.targetTouches[0].pageY - this.pageY - this.scrollPosition
                        this.top = Math.pow(diff, 0.9)
                        let ranget = diff/document.body.clientHeight*100 //计算在屏幕上滑动了多少
                        if(ranget > 20){
                            this.state = 2
                        }else if(ranget < 15){
                            this.state = 6
                        }
                        e.preventDefault()
                    }
                }else if(this.scrollState&&this.state!=4){ //向上滑动
                    this.aspect = 1
                }

            },
            touchEnd(e){
                if(this.aspect == 2&&this.state == 2||this.state == 1){ //上拉处理
                    this.top = 100
                    this.state = 1
                    this.topCallback()
                }else if(this.aspect == 2){
                    this.state = 0
                    this.top = 0
                }
            },
            onScroll(e){
                let listHeight = this.myScrollList.offsetHeight //列表总高度
                let listScrollTop = e.target.scrollTop + this.myScroll.offsetHeight //当前滚动条位置
                if(this.state == 0&&listHeight-listScrollTop < 100){
                    this.bottomCallback()
                }
                if(this.getScrollTop)this.getScrollTop(e.target.scrollTop) //返回X，Y
            },
            topCallback(){ //刷新回调
                this.onRefresh(this.state)
            },
            bottomCallback(){ //加载回调
                if(this.state != 7){
                    this.state = 4
                    this.onPull(this.state)
                }

            },
        },
        mounted(){
            this.myScroll = this.$refs.myScroll //获取滑条dom
            this.myScrollList = this.myScroll.children[1] //获取列表dom
        }
    }
</script>
<style lang="scss" scoped>
    .allow{
        overflow:hidden;
        height: auto;
    }
    .prohibit{
        max-width: 100%;
        max-height: 100%;
        height: 100%;
        overflow:hidden;
        overflow-y: scroll;
        -webkit-overflow-scrolling: touch;
        will-change: transform;
        transition: all 450ms;
        backface-visibility: hidden;
        perspective: 1000;
    }
    .my-scroll{
        position: relative;
        color: #fff;
        .scroll-top{
            text-align: center;
            display:flex;
            position:absolute;
            top:0;
            left:0;
            width:100%;
            overflow: hidden;
            div{
                display:flex;
                height:auto;
                width:100%;
                justify-content: center;
                align-items:center;
                flex-wrap: wrap;
                i{
                    flex:1 0 100%;
                    display:block;
                    height: 0.4rem;
                }
                img{
                    width:0.6rem;
                }
                p{
                    flex:1 0 100%;
                }
            }
        }
        .scroll-list{
            overflow:hidden;
            min-height: 100%;
        }
        .scroll-bottom{
            text-align: center;
            line-height: 40px;
        }
    }
</style>
